The Penobscot River in Maine has been the object of environmental concern and focus for years. It is the largest watershed in New England and hosts the largest run of Atlantic salmon on the East Coast. Despite its ecological importance, the watershed has experienced significant degradation due to high levels of mercury contamination by a chemical plant. In 1967, a pharmaceutical company, Mallinckrodt began discharging mercury into the river as part of its production process, leaving 13 tons of Mercury in the river by 1970.
Mercury is a particularly worrisome and challenging contaminant because it does not easily break down. The contamination has had a significant and lasting impact on the surrounding ecosystem and nearby communities. The state of Maine issued an advisory warning pregnant women against eating certain species harvested from the river, and certain lobster and crab fisheries have been shut down.
However, due to the steadfast and tenacious efforts of environmental advocates, this story has a silver lining. Senior attorney Nancy Marks from the NRDC (the Natural Resources Defense Council) filed a lawsuit in 1998, and after two decades of litigation, a major legal breakthrough was achieved. In 2022, the district attorney of Maine settled the long-running case, requiring Mallinckrodt to pay $197 million in remediation for the mercury damage.
Because this watershed has been the subject of extensive study to document the need for remediation, there is considerable data about its sediment history. NOAA has compiled datasets on sediment, soil, and tissue chemistry from various studies of the Penobscot watershed. Using this data, we will examine mercury levels in the sediment.
Enter questions and hypotheses here
Research Questions:
Question 1. How do mercury contamination levels change over time in the sediments in the Penobscot River? Question 2. Does mercury contamination increase with depth?
Hypothesis 1: Post closure of the site, we would expect that mercury levels in surface sediment will decrease over time and as they get further away from the site due to natural attenuation.
Hypothesis 2: Over time, mercury concentrations have decreased in the Penobscot River due to sedimentation in the river.
The dataset was generated from NOAA’s DIVER (Data Integration, Visualization, Exploration and Reporting) system, which is part of the NOAA Damage Assessment, Remediation, and Restoration Program (DARRP). The data contains Mercury results from sediment samples collected in the Penobscot River region in Maine from June 1st, 1970 to May 5th, 2021. Data is not available for every month of the years provided, likely due to shifting priorities with monitoring or project specific challenges.
| Item | Value |
|---|---|
| Data Source | NOAA DIVER |
| Date Range | June 1st, 1970 to May 5th, 2021 |
| Number of Records | 28,058 |
| Records with Coordinates | 24,501 |
## Reading layer `Penobscot_River' from data source
## `/home/guest/ENV872_EDA_FinalProject/Shapefiles/Penobscot_River.shp'
## using driver `ESRI Shapefile'
## Simple feature collection with 1 feature and 1 field
## Geometry type: POLYGON
## Dimension: XY
## Bounding box: xmin: -7667023 ymin: 5542624 xmax: -7647021 ymax: 5593963
## Projected CRS: WGS 84 / Pseudo-Mercator
We began by importing the raw NOAA Diver dataset and subsetting it to include only the columns relevant to our analysis, including site location, depth, depth type, chemical type (mercury), and concentration. Next, we flagged all records containing coordinate information and created a new subset consisting only of samples with valid coordinates. This subset was then converted into a spatial dataset for future mapping and spatial analyses.
## [1] "Station_Group_List" "Case_Activity"
## [3] "Source_Type" "Data_Classification"
## [5] "Site_ID" "Data_Source"
## [7] "Data_Category" "Sharing_Status"
## [9] "Workgroup" "Collection_Workplan"
## [11] "Gulfspill_Workplan_Name" "LOSDMS_Workplan_ID"
## [13] "Study_Name" "Study_ID"
## [15] "Component_Name" "Project_Name"
## [17] "Area_Description" "DB_Sample_ID"
## [19] "Matrix_Group" "Trip_ID"
## [21] "File_Collection_ID" "Station"
## [23] "Station_Description" "Habitat_Type"
## [25] "Date" "Hour_of_day"
## [27] "Minutes_of_Hour" "Sample_ID"
## [29] "Survey_Notes" "Sample_Notes"
## [31] "Collection_Matrix" "Collection_Method"
## [33] "Sample_Upper_Depth" "Sample_Lower_Depth"
## [35] "Sample_Depth_Unit" "Depth_Category"
## [37] "Lab_Name" "Sample_Delivery_Group"
## [39] "Analysis_Method" "Lab_ID"
## [41] "Sample_Type" "Lab_Replicate"
## [43] "Analysis_Matrix" "Analysis_Matrix_Detailed"
## [45] "Analysis_Detail" "Detection_Limit"
## [47] "Reporting_Limit" "Measurement_Basis"
## [49] "Validation_Level" "PDB_Sample_Details"
## [51] "TOC_pct" "Analysis_Type"
## [53] "Analysis" "ChemCode"
## [55] "DV_Qual_Reason" "Qualifier_Code"
## [57] "Analysis_Result_Unit" "Location_Geom"
## [59] "Max_Result_.Raw." "Start_Latitude"
## [61] "Start_Longitude" "End_Latitude"
## [63] "End_Longitude"
## Rows: 23,224
## Columns: 18
## $ Case_Activity <chr> "Penobscot River", "Penobscot River", "Penobscot …
## $ Site_ID <int> 3200, 3200, 3200, 3200, 3200, 3200, 3200, 3200, 3…
## $ Study_Name <chr> "PR EGAD Fort Point Cove Sed & Tiss 2005", "PR EG…
## $ Area_Description <chr> "FORT POINT COVE - PBFPFP", "FORT POINT COVE - PB…
## $ Matrix_Group <chr> "Sediment", "Sediment", "Sediment", "Sediment", "…
## $ Station <chr> "REP 1_FPC", "REP 2_FPC", "REP 3_FPC", "SBS-403",…
## $ Date <date> 2005-11-10, 2005-11-10, 2005-11-10, 1994-08-01, …
## $ Sample_ID <chr> "3200-24-PBFPFP REP 1", "3200-24-PBFPFP REP 2", "…
## $ Sample_Upper_Depth <dbl> -9, -9, -9, 0, 0, -9, -9, -9, -9, -9, -9, -9, -9,…
## $ Sample_Lower_Depth <dbl> -9.00, -9.00, -9.00, 60.96, 60.96, -9.00, -9.00, …
## $ Sample_Depth_Unit <chr> NA, NA, NA, "cm", "cm", NA, NA, NA, NA, NA, NA, N…
## $ Depth_Category <chr> "Subsurface Sediment", "Subsurface Sediment", "Su…
## $ Lab_Replicate <chr> "1", "1", "1", "1", "1", "1", "1", "1", "1", "1",…
## $ ChemCode <chr> "MERCURY", "MERCURY", "MERCURY", "MERCURY", "MERC…
## $ Max_Result_.Raw. <dbl> 0.23, 0.30, 0.24, 2.50, 22.00, 0.10, 19.00, 5.00,…
## $ Analysis_Result_Unit <chr> "PPM", "PPM", "PPM", "PPM", "PPM", "PPM", "PPM", …
## $ Coordinate_Flag <chr> "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y", "Y",…
## $ geometry <POINT [°]> POINT (-68.815 44.47167), POINT (-68.815 44…
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## -9.000 0.131 0.332 6.789 1.140 6494.000
## [1] "PPM" "mg/L"
## [1] NA "cm"
After cleaning the dataset, we plotted sample depths against mercury concentrations, mapped the sampling locations onto the Penobscot River, and examined concentration trends over time. We plotted a reference line representing the mercury PEC, above which harmful effects to sediment-dwelling biota are likely to occur.